The present invention relates to a micromechanical component having a substrate an a movable sensor structure in a first micromechanical functional layer on the sacrificial layer. The present invention also relates to a corresponding manufacturing method.
Although it is applicable to any micromechanical components and structures, in particular to sensors and actuators, the present invention and the underlying problem are elucidated with reference to a micromechanical component, e.g., an acceleration sensor, that is manufacturable using silicon surface micromechanical technology.
Monolithically integrated inertial sensors manufactured by surface micromechanical technology in which the sensitive movable structures are situated on the chip without protection (analog devices) are generally known. This results in increased expenses for handling and packaging.
This problem may be circumvented by a sensor, the structures manufactured by surface micromechanics being covered by a second cap wafer. This type of packaging is responsible for a large share (approximately 75%) of the cost of manufacturing an acceleration sensor by surface micromechanical. These costs arise as a result of the high surface area requirements of the sealing surface between the cap wafer and the sensor wafer and due to the complex structuring (2–3 masks, bulk micromechanics) of the cap wafer.
The structure of a functional layer system and a method for hermetic capping of sensors using surface micromechanics is described in German Patent Application 195 37 814 A1. The manufacture of the sensor structure using known technological methods is explained. The cited hermetic capping is performed using a separate cap wafer made of silicon, which is structured using expensive structuring processes such as KOH etching. The cap wafer is applied to the substrate with the sensor (sensor wafer) using a seal glass. This requires a wide bonding frame around each sensor chip to ensure an adequate adhesion and sealing ability of the cap. This limits the number of sensor chips per sensor wafer considerably. Due to the large amount of space required and the expensive manufacture of the cap wafer, sensor capping incurs considerable costs.